1. Field
The present disclosure relates generally to actuators, more specifically, to piezoelectric bimorph actuators encased in an insulating shell to ensure that the actuator is substantially moisture impervious.
2. Description of the Related Art
Bimorphs are piezoelectric elements which change their shape under application of electrical energy. Bimorphs are widely used in a variety of actuators, such as in shutter mechanisms of cameras, head assemblies of hard drive disks, etc. In particular, bimorph type actuators are also used in gas transducers. Gas transducers are utilized in a variety of industries, such as pipeline, chemical, distillery, food processing, petrochemical, pharmaceutical and other industries where precise control of various valves and other equipment is desired. Gas transducers operate by controlling gas flow and/or pressure, which in turn actuates other equipment (e.g., valves, louvers, etc.). However, use of piezoelectric bimorph actuators where the gas stream may contain a significant amount of moisture can be problematic. High moisture content degrades the bimorph actuators, wherein the bimorphs develop electrical problems and in certain situations stop functioning altogether (e.g., arcing across energized regions of the bimorph). More particularly, electrical malfunction is especially dangerous when bimorph actuators are used in combustible atmosphere (e.g., natural gas)—electrical arcing may result in ignition.
Attempts have been made to create moisture-proof piezoelectric bimorph actuators which are insulated to prevent arcing. However these attempts generally involved actuators having bonded monolithic packaging requiring that the actuator deform the entire packaging to operate. Furthermore, in gas transducers, operating temperatures range from about −40 to about 150 degrees Fahrenheit. The extreme temperatures expand and contract the packaging thereby constricting movement of the bimorph as well. This imparts a significant strain upon the actuator rendering the device inoperable.
Therefore, there is a need for a free-floating piezoelectric bimorph actuator which is substantially moisture impervious and electrically insulated as well as protected from extraneous strain stemming from deleterious effects of a monolithically formed bimorph package.